A netbook is as good as the programs are you run on it. Most come with pre-installed software but if you want to be as effective as you can, it's often suggested that you get some better solutions. I've been using my 10 "netbook for more than half a year and here are the top 4 software I found during that time.
1. Opera browser. I do not like the default Internet Explorer that comes with Windows XP, because it starts slowly, pages render slow and it's hardly following W3C standard causing more work for webmasters and errors on pages for me. I change between Chrome and Opera using them both about for the same amount of time. Chrome's tab bar and menu bar is more netbook friendly because it's gentle on vertical space, and Opera is just fast. You can use Firefox too but I find it ridiculous for a browser to eat up 5-600 megabytes of the available 1GB memory with 2 open tabs.
2. I still use the old MSN Messenger that comes with XP, reason being that Windows Live Messenger loves to crash on me and use the processor for no good reason. It might be a fluke of error, something with my installation or general bad luck, but I rather not use my webcam than sacrifice 2 hours of my battery on an instant messaging client.
3. Foxit PDF reader. It's small, blazing fast and I can read my e-books in it, what else should I use my PDF reader for? I still can not get my head around Adobe Reader's 100 ~ ish MB size. Did I mention that it's fast and free? There are some missing features, but the basic things are there and you can always install Adobe Reader when you run into something that's not included.
4. Paint.net. Go ahead and get paint.net if you want to get some photo editing done for free. There are dozens of different plugins for it but it does everything you need out of the box as well. Red-eye removal, image resizing, filters, effects, layers and everything more expensive image manipulation software do, with the difference that it comes at no cost.
It's just too easy to waste resource in a Windows environment and netbooks are even more pre to getting swamped by swarms of different applications you pick up along the way trying to use the same stuff you do on your desktop system. Please keep in mind that these little laptops are not for heavy use and applications need to be chosen accordingly.